aco___ofdm系统信道估计算法的研究大学生毕业论文（设计）.doc

设计（论文）题目：  摘 要 ACO-OFDM无线光通信系统中，为了能达到系统需要的解码要求，必须要进行准确的信道估计。针对ACO-OFDM系统中，系统信号均值大于零，不满足传统叠加周期序列信道估计方法所要满足的数据信号序列均值为零的条件的问题，本文通过对传统方法在训练序列和本地矩阵的生成等方面进行改进，提出一种适用于该系统的基于叠加训练序列的信道估计方法。该方法首先通过对复数序列进行共轭对称变换、IFFT、并串变换、限幅和拆分组合，生成单极性非负周期实序列；然后根据接收信号的时域统计特性和功率分配因子的取值，合理地设计本地矩阵；通过对接收信号进行一阶统计平均处理，完成信道估计。 与传统的叠加周期序列的信道估计方法相比，本文提出的方法能直接应用于光强度调制的ACO-OFDM系统中，并且通过将训练序列与数据在一段时间间隔内同时传送，不需要额外的频段和时隙传输已知训练序列，保证了系统的传输效率，同时算法复杂度较低，时间功率分配相对灵活，具有显著的优势。结合理论分析，并通过计算机仿真表明，该信道估计方法的性能与系统子载波数目、功率分配因子以及信噪比有着密切的关系。若功率分配因子保持不变，随着系统子载波数目的增大，MSE逐渐减小，估计性能就越好。随着功率分配因子的增大，训练序列的能量增大，信道估计性能越好，精度越高，验证了该算法的有效性。 【关键词】  ABSTRACT In ACO-OFDM wireless optical communication system, it is necessary for achieving good decode performance to estimate accurately channel characteristic parameters. In ACO-OFDM system, the mean of the data is not zero. That cannot satisfy the qualification in the traditional channel estimation method using superimposed periodic training, which is zero-mean of the data sequence. Via the improvement on the training sequence and the local matrix, a channel estimation method for ACO-OFDM based superimposed training is proposed in this paper. Firstly, the unipolar non-negative periodic real sequence is generated through doing the conjugate symmetry transform, IFFT, parallel-to-serial conversion, clipping, splitting and composing complex sequence. Secondly, according to statistics of the received signal in time domain and the power allocation factor, the local matrix is designed rationally. Thirdly, the first-order statistic of the received signal in time domain is used to estimate the channel finite-impulse response. Compared with the channel estimation methods of traditional superposition of periodic sequences, the proposed method can be applied directly to optical intensity modulation ACO-OFDM systems. It transmits the training sequence and data over a period of time interval at the same time. It is dont need the extra frequency and time slot to transmit the known training sequence, th